The detection of the reproductive status of animals is highly desirable for farmers. It is especially desirable for a farmer to know when individual cows in a herd are ‘in heat’. The early detection of cows in heat allows the farmer to improve his livestock by selective breeding and to better plan his business operations. This can be achieved by mating selected animals, using artificial insemination or any other suitable method. When using any of these methods, it is necessary to determine accurately and reliably when cows are in heat so that the cows in heat can be singled out and inseminated. The heat cycle of cows is active only for a short period of time and hence detection and insemination must be done within this period.
Various methods have been used in the prior art for the detection of cows ‘in heat’. The most common method of detection used is visual observation whereby cows seen to allow mounting by other cows are separated from the herd by a farmer. However the farmer must quickly identify and mark the cows in heat since the heat cycle of a cow only lasts for a short period of time as mentioned above. This may be difficult in a large herd as cows are generally widely dispersed and 24 hour observation may be impossible. Therefore this method is time consuming, depends on the attentiveness and skill level of the farmer and, accordingly, the heat cycle of many cows may go undetected.
Another frequently used method of detection involves the application of paint on the tail-bone of a cow, where the subsequent smudging of this paint indicates that the cow was mounted by another animal. This method involves a skilled farmer closely observing each animal in order to detect which animals have been mounted and hence it is also very time consuming and is not very reliable in harsh weather conditions.
An alternative method is to use indicators on the backs or rumps of cows that are set off when other animals mount the cows in heat. In most cases, these methods incorporate some form of visual indicator such as a reflective device/tag that becomes exposed when mounting occurs or some sort of fluid reservoir that becomes discharged when mounting occurs. This means that these indicators still require some form of visual observation and interpretation by a skilled farmer in order to identify the animals in heat and hence the heat cycles of some animals of a large herd may still be missed due to delays or inaccuracies in checking.
Complicated systems incorporating image capture devices and software that interpret images using various algorithms have been developed so that the observation and interpretation of the indicators/tags is fully automated. However these ‘automated visual detection systems’ have some external requirements in order to function properly, such as suitable lighting conditions, exact positioning and ‘line of sight’ viewing for image capturing. Furthermore they include hardware that is expensive (digital cameras, computers, lighting systems, etc), is sensitive to fouling, dust or dirt and includes software interpretation modules that can be inherently difficult to develop to an accepted state of reliability. Also, the indicators/tags used in these systems frequently get covered in manure, dirt and other contaminants which make visual image processing error prone. Therefore a system which is completely insensitive to these types of disadvantages is required.
International Patent Application Number PCT/NZ2011/000097 describes a prior art system in which a tag able to transmit an electronic signal is attached to an animal. When another animal mounts the animal carrying the tag, an abradable layer is removed from the tag by one animal rubbing against the other. The whole or partial removal of the abradable layer alters the ability of the detection tag to transmit a signal, or it alters a characteristic of the signal, so that animals that have been mounted can be detected by a suitable signal receiver.
One problem with this system is that it is difficult to distinguish between an animal with a missing tag (e.g. the tag has fallen off) and an animal with an inactive tag because, in both cases, no signal is received. It would be desirable to be able to identify animals with missing tags in a different way to identifying animals with inactive tags.
PCT/NZ2011/000097 attempts to solve this problem using a tag in which the length of the antenna is changed when the tag is activated by a mounting animal so that the signal changes in frequency on activation. However this technique is prone to error if, for example, on activation, the length of the antenna only changes enough to alter the signal's frequency a small amount.
In another example, PCT/NZ2011/000097 describes the use of an “always-active” tag together with a tag that can be activated when the animal is mounted. However this system requires multiple tags on one animal and is therefore inefficient and costly. In addition, the presence of an always-active tag does not prevent the tag that can be activated from falling off.
In the prior art, once the cows ‘in heat’ have been identified, they are separated from the herd (referred to as ‘drafting’) for further treatment, e.g. artificial insemination. This drafting process is done either manually by a farm-worker handling a gate, or at various levels of automated drafting by automatically switching a gate when the cow concerned is present. Usually the drafting process is done during or after milking of the cow when the cow leaves the milking parlour through the exit race.
According to current farming practice, drafting is carried out using a three step process. The first step involves a skilled worker identifying the cows through visual identification. The second step involves manual or automated marking of cows. Manual marking of cows is done with, for example, shaving cream. In an automated system a cow ID is entered into a computer program instead of marking the cow with shaving cream. Typically this marking is done on cows when they enter the milking shed/platform.
The third step of drafting is carried out while the cows are exiting the milking platform by switching one or more gates. In the case of manual selection, a gate operator operates the gate when a marked cow (i.e.: a cow having shaving cream on its back) is seen at the gate entrance. In the case of automated selection, the system reads the cow ID when the cows are in the exit race (using a tag reader of a prior art animal identification system, e.g. RFID ear-tags used for identification of cows). After reading the cow's ID the automated system checks if the read cow ID was previously entered into the computer in step two and operates the gate accordingly.
The above described manual and automated methods of drafting have disadvantages similar to the methods used for detection of ‘heat’ in animals. For example manual visual drafting may not be accurate in a farm with a large herd of animals and automated drafting requires expensive hardware and software.
In other situations, animals may be selected while they are held in a stall, pen or race, for example when an inspector selects lambs that are suitable to go to the meat works. In such cases a visual mark is placed on the selected animals and those animals are drafted out manually. The operation takes a number of staff since some are required to encourage the animals through the drafting gates, while another controls the gates.
PCT/NZ2011/000097 describes improved drafting processes but these have disadvantages consequential to the disadvantages of the tags as discussed above. For example, if the detection tag has fallen off an animal that is ‘in heat’, the animal might be drafted incorrectly.